1. Field of the Invention
The present invention relates to an electromagnetic release device, and particularly to device employing a combination magnet including a magnet core, a permanent magnet and an elctromagnet coil in operatively associated relation.
2. Description of the Prior Art
In an electromagnetic shutter release device of the type in which the shutter is released as an armature is retracted or moved away from a magnetic core by a shutter releasing operation, the armature is spring biased toward quick disengagement from the core in order to ensure that the releasing action will immediately occur with the shutter releasing operation. Since the armature will accordingly remain disengaged from the core after each shutter release, it is necessary to reset the armature into engagement with the core. This reset action has been accomplished either with a member of a camera mechanism in association with a subsequent shutter charging or cocking operation or otherwise in association with an exposure terminating operation.
However, in the former case mentioned above, the core remains apart from the armature for the while until the sequent shutter charging operation is performed so that there are dangers such that dust or foreign matters get between these members, and that these members are damaged.
In order to prevent these dangers, it may be considered that these members are sealed by means of a case and the like, but such measures will inevitably complicate the structure, and failing to meet with practical purposes.
Meanwhile, in the latter case mentioned above, although generally less dangerous than the former case, but similar dangers are still likely to be caused in the case of recently developed cameras with an electronic shutter in which a very long exposure time is often set.
For the purpose of overcoming the above disadvantages of conventional devices, a device which accomplishes the reset action in relation with the shutter releasing action has been proposed in U.S. Pat. No. 4,133,608.
In the case of the device disclosed in this U.S. Patent, the armature 6 is reset by engaging with the core 4a by engaging the bent portion 11b of the release sensor 11 with the resetting projection 9b, and the shutter opening is initiated by the engagement of the raised portion 11a provided at the other end of the sensor 11 with the lock lever 12. Therefore, this prior art device still is confronted with disadvantages that the armature cannot be reset only simultaneously with or after the initiation of the opening operation of the shutter, so that the above mentioned reset action is retarded.
That is, in the device of U.S. Pat. No. 4,133,608, when the armature 6 is reset on the core 4a by the rightward movement of the sensor 11, the bent portion 11b of the sensor 11 is locked on the resetting projection 9b, and thus is prohibitted to make a further rightward movement so that it is impossible to release the engagement of the lock lever 12 after the armature 6 is reset on the core 4a.
Therefore, in the device according to U.S. Pat. No. 4,133,608, it is impossible to perform the reset action before the initiation of the shutter opening operation, so that this prior art device still has some possibility of danger that the reset action is retarded and dust or foreign matters come into between the members and damage the members as mentioned hereinbefore.
Further, due to the structure as mentioned before, the device of the U.S. Patent has a problem that the armature 6 in some cases fails to engage with the core 4a or in other cases severely strikes the core 4a depending on the accuracy of the resetting projection 9b. Therefore, in this prior art, it is necessary to precisely work the resetting projection 9b.